1. Field of the Invention
This invention relates to rigid end plugs for tubular containers and more particularly to axially inserted rigid end plugs forming locking closures and providing rigidity and strength to tubular containers formed from sheet material.
2. Description of the Prior Art
In my above mentioned co-pending application entitled: "End Caps For Containers And Their Manufacture," I previously described that it is known in the packaging art to fabricate tubular containers having flexible sides and rigid end caps. The flexible sides are normally a thermo-plastic material approximately 0.010 to 0.050 inches in thickness, and manufactured in the form of a tube. The tube may be given any desired cross-sectional shape such as an ellipse, circle, or polygon, and is then held techniques the desired shape by the rigid end caps. Various tecnhiques have been employed in the joining of rigid end caps to the flexible sides including the use of adhesives, tape, staples and other fastening materials. Another known technique is to provide an end cap structure for frictionally engaging the thin flexible sides. In most applications, however, frictional engagement is inadequate and a positive locking engagement is required. There is no known prior art technique suitable for providing a container of the type disclosed herein that is either permanently closed or easily reopenable. Moreover, prior art manufacturing techniques do not lend themselves to a one-step assembly by either hand or machine, for providing a positive engagement between flexible sides and rigid end caps.
In my above named co-pending application, I disclosed a revolutionary end cap structure in which opposed camming surfaces firmly locked into the perforations of an axially inserted tube. In some applications, however, it is desirable to use locking means other than the previously disclosed opposed camming surfaces.